Methods for extracting strengthened glass substrates from glass sheets
Methods for extracting strengthened glass substrates from glass sheets are described herein. In one embodiment, the method for extracting strengthened glass substrates from glass sheets comprises forming a plurality of channel segments in the glass sheet. The plurality of channel segments may extend through the thickness of the glass sheet and are separated by remnant glass webs connecting the glass substrate to the glass sheet. The plurality of channel segments extend around a perimeter of the glass substrate. Thereafter, the glass sheet is strengthened by ion-exchange. The glass substrate is then separated from the glass sheet by severing the glass substrate from the remnant glass webs.
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1. Field
The present specification generally relates to methods for extracting glass substrates from glass sheets and, more specifically, to methods for extracting strengthened glass substrates from glass sheets.
2. Technical Background
Thin glass substrates have a variety of applications in consumer electronic devices. For example, such glass substrates may be used as cover sheets and/or touch screens for LCD and LED displays incorporated in mobile telephones, GPS devices, display devices such as televisions and computer monitors and various other electronic devices. As use the use of glass substrates in various devices continues to expand, the geometric complexity of the glass substrates also increases. For example, certain applications may require that the glass substrates be formed with complex shapes, such as curved peripheries and/or through-features, thus requiring additional machining operations to achieve the desired geometry.
The glass substrates may be formed by separating a glass sheet into a plurality of discrete glass. The glass sheet may formed from damage resistant glass, such as ion-exchanged glass or similarly strengthened glass. For example, the ion-exchange process creates a compressive stress at the surfaces of the glass substrate. These compressive stresses extend beneath the surface of the glass substrate to a certain depth, referred to as the depth of layer. The compressive stresses are balanced by a layer of tensile stresses (referred to as central tension) such that the net stress in the glass substrate is zero. The formation of compressive stresses at the surface of the glass substrate counters crack propagation in the compressive layer and, as such, mitigates catastrophic failure of the glass substrate for flaws which do not extend through the depth of layer.
However, strengthened glass substrates are susceptible to edge damage, especially after the glass substrates are separated from a glass sheet after the strengthening process has been performed. More specifically, separating the glass substrate after ion-exchange processing leaves the central tension layer exposed at the edges of the glass substrate, thereby leaving the edge susceptible to damage which may lead to catastrophic failure.
Moreover, when a glass substrate is intended for use as a touch screen, electrically conductive coatings may be applied to the glass substrate. Such coatings are commonly applied to a glass sheet prior to separating the glass sheet into a plurality of discrete glass substrates. However, these coatings are not able to withstand the ion-exchange process, thus compounding the aforementioned problems.
SUMMARYAccording to one embodiment, a method of extracting a strengthened glass substrate from a glass sheet includes forming a plurality of channel segments in the glass sheet. The plurality of channel segments extend through the thickness of the glass sheet and the channel segments are separated from each other by remnant glass webs connecting the glass substrate to the glass sheet. The plurality of channel segments extend around a perimeter of the glass substrate. Thereafter, the glass sheet is strengthened by ion-exchange. The glass substrate is then separated from the glass sheet by severing the glass substrate from the remnant glass webs connecting the glass substrate to the glass sheet.
In another embodiment, a method of separating an ion-exchange-strengthened glass substrate from a glass sheet includes strengthening the glass sheet by ion-exchange. Thereafter, a coating material is applied to the glass sheet. The glass sheet is then segmented into a plurality of glass substrates along straight parting lines. At least one curved feature is formed in the glass substrate after the glass substrate is separated from the glass sheet. The perimeter of the glass substrate is then finished such that the perimeter of the glass substrate is in compression.
In yet another embodiment, a glass substrate for use as a cover glass with touch screen functionality includes an ion-exchanged glass having a first surface, a second surface opposite the first surface, and a perimeter. The perimeter includes at least one curved feature along a length of the glass substrate, the at least one curved feature having a maximum radius of curvature of less than 10 mm. The perimeter may be under compression. An optically-transparent and electrically-conductive coating may be applied to at least one of the first surface or the second surface. The glass substrate may be formed by a process which comprises: strengthening a glass sheet by ion-exchange; applying an optically-transparent and electrically-conductive coating material to the glass sheet; separating the glass substrate from the glass sheet; and finishing the perimeter of the glass substrate such that the perimeter is under compression.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part, will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate the various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter.
Reference will now be made in detail to various embodiments of methods for extracting strengthened glass substrates from glass sheets.
Referring now to
Referring to
In the embodiments described herein, the channel segments 104 may be formed in the glass sheet 100 using a variety of techniques. For example, in one embodiment, the channel segments 104 may be formed by laser processing, such as laser ablation or laser through-cutting. In another embodiment, the channel segments 104 may be formed in the glass sheet 100 by a machining operation, such as computer numeric control (CNC) machining, or a similar machining process. In yet another embodiment, the channel segments may be formed with an etching process, such as when the pattern of the channel segments 104 is masked and a chemical etchant is applied to the glass sheet 100 to remove the glass in the channel segments 104. In still another embodiment, the channel segments may be formed by water jet cutting. In yet another embodiment, a combination of techniques may be used. For example, in one embodiment, the channel segments may be formed by water-jet cutting and, thereafter, CNC machining may be used to finish the sides of the channel segments and form chamfers and/or bevels in the edges of the glass substrate. While specific techniques for forming the channel segments 104 in the glass sheet are referenced herein, it should be understood that other techniques may also be employed.
The channel segments 104 are formed in the glass sheet 100 such that the channel segments 104 form at least one curved feature in the perimeter 116 of the glass substrate 102. For example, in the embodiment shown in
While the embodiments shown in FIGS. 1A and 2A-2B depict a curved feature forming a corner 117 of the glass substrate 102, it should be understood that various other curved features may be formed in the perimeter of the glass substrate 102. For example, the curved feature may be formed along the perimeter 116 of the glass substrate 102 in a location other than the corner 117, such as when one or more curved features are formed in the perimeter 116 of the substrate along a length of the glass substrate 102. In one embodiment, the maximum radius of curvature of the curved feature is less than about 10 mm. In another embodiment, the maximum radius of curvature of the curved feature is 5 mm or less or even 2 mm or less. However, it should be understood that curved features having a maximum radius of greater than or equal to 10 mm may also be formed in the glass substrate 102.
Moreover, in one embodiment, the channel segments 104 are formed in the glass sheet 100 such that a chamfer or bevel is formed at the intersection of the perimeter 116 of the glass substrate 102 with the top surface 114 and the bottom surface 115 of the glass substrate 102. For example, referring to
Referring now to
The remnant glass webs 106 between the channel segments 104 have the same thickness as the remainder of the glass sheet 100 in the embodiment depicted. However, in other embodiments, the remnant glass webs 106 may have a thickness which is less than the thickness of the remainder of the glass sheet 100. For example, referring to
Forming the channel segments 104 in the un-strengthened glass sheet 100, as described herein, reduces cracking or chipping of the glass substrate, particularly in areas adjacent to the perimeter 116 of the glass substrate 102 where the substrate is most susceptible to damage both during machining of ion-exchanged glass and during subsequent use of the glass substrate. Moreover, forming the channel segments in the un-strengthened glass sheet exposes the perimeter edge of the glass substrate which, in turn, facilitates chemically strengthening the perimeter of the glass substrate 102 in a subsequent processing step while the glass substrate 102 remains attached to the glass sheet 100.
In one embodiment, the initial step of the method for extracting a glass substrate 102 from a glass sheet 100 may further comprise forming additional through-features 120a, 120b, 120c in the glass substrate 102, as shown in
It should be understood that the formation of through-features in the glass substrate 102 of the glass sheet 100, in addition to the channel segments 104 is optional. For example, in one embodiment, the glass substrate 102 of the glass sheet 100 may be formed without through-features while in other embodiments one or even a plurality of through-features may be formed in the glass substrate 102 of the glass sheet 100 in addition to the channel segments 104.
In one embodiment, the glass sheet 100 may be annealed before formation of the channel segments 104 and through-features to reduce or eliminate residual stresses present in the glass sheet which may lead to cracking or chipping of the glass sheet during formation of the channel segments 104 and/or through-features. Alternatively or additionally, the glass sheet 100 may be annealed after formation of the channel segments 104 and through-features. The annealing step may be utilized to reduce stresses that develop in the glass sheet 100 during formation of the channel segments and/or through-features. For example, where laser processing is used to form the channel segments of the through-features, thermal stresses may remain in the glass sheet following processing. The annealing step may be utilized to relieve these residual stresses such that the glass sheet 100 (including the glass substrate 102) is substantially stress-free. In order to anneal the glass sheet 100, the glass sheet may be heated to the annealing point of the glass (i.e., to a temperature where the dynamic viscosity of the glass is about 1×1013 Poise). However, it should be understood that the annealing step is optional and that, in some embodiments, the glass sheet may be strengthened after formation of the channel segments and through-features without first undergoing an annealing step.
Still referring to
In the embodiments described herein, the compressive stress and depth of layer developed in the glass sheet 100 and glass substrate 102 by strengthening are sufficient to improve the damage tolerance of the glass substrate 102 while also facilitating further processing (such as by machining or laser processing) without risk of introducing flaws into the substrate. In one embodiment, the compressive stress may be from about 200 MPa to about 1000 MPa. In another embodiment, the compressive stress may be from about 500 MPa to about 800 MPa. In yet another embodiment, the compressive stress may be from about 650 MPa to about 900 MPa. In one embodiment, the depth of layer D may be from about 10 microns to about 80 microns. In another embodiment, the depth of layer D may be from about 30 microns to about 60 microns. In yet another embodiment, the depth of layer D may be from about 40 microns to about 60 microns.
While specific reference has been made herein to use of an ion-exchange strengthening process in which sodium ions are replace with potassium ions, it should be understood that the specific ion exchange process utilized to strengthen the glass sheet is dependent on the composition of the glass from which the glass sheet is formed. For example, other ion-exchange processes may be utilized in which different ions are exchanged in order to strengthen the glass, such as when lithium ions and/or other alkali ions are exchanged for sodium ions in the ion-exchange processes to achieve the desired compressive strength and depth of layer. Accordingly, it should be generally understood that, during ion-exchange, a smaller ions in the glass are exchanged with larger ions to achieve the desired compressive stress and depth of layer. Moreover, the chemical strengthening process may be a single-ion-exchange process or an ion-exchange process in which multiple ions are exchanged to produce a complex diffusion profile (e.g., a double-ion-exchange process).
Referring now to
In one embodiment, the channel segments 104 and the through-features (when present) are optionally plugged with a filler material 112 which fills and conforms to the shape of the channel segments 104 and the through-features. For example, the filler material 112 may be a UV-curable polymer resin or a thermally curable polymer resin which is deposited in the channel segments 104 and through-features. The polymer resin is then cured to solidify the resin and thereby improve the mechanical strength of the glass sheet 100 during subsequent processing. Alternatively, the filler material 112 may be a frit material, such as a glass frit or ceramic frit, which is deposited in the channel segments 104 and through-features as a paste and thereafter cured (i.e., dried) to solidify the paste thereby improving the mechanical strength of the glass sheet 100. In yet another embodiment, the filler material 112 may be a wax-based material which is initially deposited in the channel segments 104 and the through-features as a liquid and then solidified, such as by cooling, to improve the mechanical strength of the glass sheet 100.
In another embodiment (not shown), the channels segments 104 and the through-features (when present) may be plugged by applying a film to the top and bottom surfaces of the glass sheet 100 such that the channels segments 104 and the through-features are covered. For example, a polymer film, such as a polyethylene film or similar polymer material, may be removably applied to the surfaces of the glass sheet 100 with an adhesive material such that the film covers the channel segments and the through-features. The film may be selectively applied to the glass sheet 100 such that only those portions of the glass sheet 100 having channel segments 104 and/or through-features are covered, thereby allowing other films and/or coating materials to be applied to the uncovered portions of the surface.
When a filler material is used to plug the channel segments 104 and the through-features, it should be understood that the filler material 112 should be selected such that the filler material 112 can be easily removed from the glass sheet 100 without imparting significant mechanical stress on the glass sheet 100 or the glass substrate 102. However, it should be understood that plugging the channel segments 104 is optional and, in other embodiments, the glass sheet 100 may be further processed without plugging the channel segments 104 and the through-features.
Referring now to
While one embodiment of the method for extracting a glass substrate from a glass sheet is described herein as comprising the step of applying a coating material to the glass sheet, it should be understood that this step is optional and that, in other embodiments, the glass substrate may be extracted from the glass sheet without applying a coating material to the glass sheet.
Referring now to
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In one embodiment, the localized thermal energy applied to the substrate is sufficient to both strengthen the perimeter 116 of the glass substrate 102 and to make the perimeter 116 of the glass substrate 102 molten such that the portion of the perimeter 116 with the exposed layer of central tension is reshaped to correspond to the bevels or chamfers formed in the remaining portions of the perimeter 116. The process of imparting thermal energy may be specifically tailored to the thickness and composition of the glass substrate in order to achieve the desired amount of strengthening (i.e., compressive stress and depth of layer) as well as the desired perimeter geometry (i.e., a bevel or chamfer having the desired geometry). However, to both strengthen the glass substrate by increasing the depth of diffusion of the alkali ions and reshape the perimeter of the glass substrate, the glass substrate should be heated to the working point of the glass substrate (i.e., to a temperature where the dynamic viscosity of the glass is about 1×104 Poise). The viscosity of the glass at the working point is sufficiently low to enable viscous flow of the glass which, in turn, facilitates reshaping the perimeter of the glass to a desired shape. Moreover, the temperature of the glass at the working point is more than sufficient to enable ions already in the glass to diffuse further into the substrate in the heated area, thereby strengthening the heated area.
In the embodiments described herein, localized thermal energy may be imparted to the perimeter 116 by any one of a variety of techniques including, without limitation, flame-polishing, laser heating, radiant heating, controlled dielectric discharge and various combinations thereof. For example, in the embodiment depicted in
Referring now to
Referring to
While one embodiment of the method for extracting a glass substrate from a glass sheet is described herein as comprising the step of applying a coating material to the glass sheet, it should be understood that this step is optional and that, in other embodiments, the glass substrate may be extracted from the glass sheet without applying a coating material to the glass sheet.
Referring to
Referring now to
While the embodiments shown in FIGS. 3B and 2A-2B depict a curved feature forming a corner 117 of the glass substrate 102, it should be understood that various other curved features may be formed in the perimeter of the glass substrate 102. For example, the curved feature may be formed along the perimeter 116 of the glass substrate 102 in a location other than the corner 117, such as when one or more curved features, such as curved or rounded corners, are formed in the perimeter 116 of the substrate along a length of the glass substrate 102. In one embodiment, the maximum radius of curvature of the curved feature is less than about 10 mm. In another embodiment, the maximum radius of curvature of the curved feature is 5 mm or less or even 2 mm or less. However, it should be understood that curved features with a maximum radius greater than about 10 mm may also be formed in substrate.
In one embodiment, through-features 120a, 120b, 120c may also be formed in the glass substrate 102, as depicted in
The formation of through-features in the glass substrate 102 of the glass sheet 100 is optional. For example, in one embodiment, the glass substrate 102 of the glass sheet 100 may be formed without through-features while in other embodiments one or even a plurality of through-features may be formed in the glass substrate 102 of the glass sheet 100.
As described hereinabove, the glass sheet 100 depicted in
Referring to
In the various examples of the methods for extracting shaped glass substrates from glass sheets shown and described herein, a single strengthened glass substrate is depicted as being extracted from a glass sheet. However, it should be understood that the techniques described herein may be utilized to extract multiple strengthened glass substrates from a single glass sheet. Accordingly, it will be understood that the methods described herein may be scaled to improve efficiency and economy.
It should now be understood that the methods described herein may be used to extract a strengthened glass substrate from a glass sheet such that the strengthened glass substrate has the desired resistance to damage, particularly around the perimeter of the strengthened glass substrate. At least a portion of the perimeter of the strengthened glass substrate includes a curved feature while one or more through-features may be formed through the thickness of the strengthened glass substrate. In some embodiments, the strengthened glass substrate may also comprise a coating material to enable touch functionality. The strengthened glass substrates extracted using the methods described herein have improved resistance to failure, particularly failures emanating from the perimeter of the shaped glass substrate.
It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus, it is intended that the specification cover the modifications and variations of the various embodiments described herein, provided such modification and variations come within the scope of the appended claims and their equivalents.
Claims
1. A method of extracting a glass substrate from a glass sheet, the method comprising:
- providing an un-strengthened glass sheet having a defined thickness,
- forming a plurality of channel segments in the un-strengthened glass sheet, wherein the plurality of channel segments extend through the entire thickness of the glass sheet, wherein the plurality of channel segments are separated from each other by remnant glass webs connecting the glass substrate to the glass sheet, and wherein the plurality of channel segments and the plurality of remnant glass webs extend around and collectively define a perimeter of the glass substrate;
- strengthening the un-strengthened glass sheet and the connected glass substrate by ion-exchange to produce a strengthened glass substrate connected to a strengthened glass sheet; and
- separating the strengthened glass substrate from the strengthened glass sheet by severing the strengthened glass substrate from the remnant glass webs.
2. The method of claim 1, further comprising applying a coating material to the glass sheet after the glass sheet is strengthened and before the strengthened glass substrate is separated from the strengthened glass sheet.
3. The method of claim 2, wherein the coating material comprises an optically-transparent and electrically-conductive material.
4. The method of claim 2, wherein the coating material is indium tin oxide or aluminum zinc oxide.
5. The method of claim 2, further comprising plugging the plurality of channel segments prior to applying the coating material to the strengthened glass sheet.
6. The method of claim 1, further comprising forming a through-feature in the un-strengthened glass substrate.
7. The method of claim 1, further comprising:
- forming bevels or chamfers in the perimeter of the glass substrate adjacent to the plurality of channel segments as the channel segments are formed in the un-strengthened glass sheet; and
- forming bevels or chamfers in the perimeter of the glass substrate adjacent the remnant glass webs, wherein the bevels or chamfers in the perimeter of the glass substrate adjacent to the remnant glass webs have the same geometry and dimensions of the bevels or chamfers formed in the perimeter of the glass substrate adjacent to the plurality of channel segments.
8. The method of claim 1, wherein the remnant glass webs have a thickness which is less than the thickness of the un-strengthened glass sheet.
9. The method of claim 1, further comprising finishing the perimeter of the strengthened glass substrate such that the perimeter of the glass substrate is under compression.
10. The method of claim 9, wherein finishing the perimeter of the strengthened glass substrate comprises heating the strengthened glass substrate to at least a softening point of the glass substrate.
11. The method of claim 9, wherein finishing the perimeter of the strengthened glass substrate comprises reshaping the perimeter of the glass substrate by heating the strengthened glass substrate to at least a working point of the glass substrate.
12. The method of claim 1, further comprising annealing the un-strengthened glass sheet after forming the plurality of channel segments in the un-strengthened glass sheet and before strengthening the glass sheet.
Type: Grant
Filed: Aug 26, 2010
Date of Patent: Mar 12, 2013
Patent Publication Number: 20120052252
Assignee: Corning Incorporated (Corning, NY)
Inventors: Jeffrey Todd Kohli (Corning, NY), Robert Sabia (Corning, NY)
Primary Examiner: Jason L. Lazorcik
Application Number: 12/868,927
International Classification: C03C 15/00 (20060101); C03B 33/02 (20060101);